The proposed studies are aimed at carrying out the following research program: 1) continue our investigation on the ontogenetic development of the intrinsic and neurohumoral control of cardiovascular functions throughout intrauterine life, during the neonatal period and up until the adult, nonpregnant-state pattern of control becomes evident; these studies will be attacked by in vivo and in vitro approaches; 2) the behavior of the mechanisms controlling cardiovascular functions during some forms of stress such as hypovolemia, hypoxia and bacterial infection; 3) the modifications in the neurohumoral and intrinsic control of the peripheral circulation introduced by pregnancy, including the role of sex steroid hormones; 4) the relationship between uteroplacental circulation and production of progesterone with emphasis on the role of uterine vasodilatation produced by estrogen.